# Ohm's Law & Power Calculator: Formula Conversions, Concept Guides, Law Reference, Stack Guides, Multimeter Reference

For the full tool, see: [https://capytoolkit.com/tools/math/ohms-law/](https://capytoolkit.com/tools/math/ohms-law/)

## Ohm's Law & Power Calculator: Conversions
[Volts to Amps (given Resistance) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#volts-to-amps-given-resistance): Convert Volts to Amps (given Resistance).
[Amps to Volts (given Resistance) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#amps-to-volts-given-resistance): Convert Amps to Volts (given Resistance).
[Volts to Ohms (given Current) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#volts-to-ohms-given-current): Convert Volts to Ohms (given Current).
[Amps to Ohms (given Voltage) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#amps-to-ohms-given-voltage): Convert Amps to Ohms (given Voltage).
[Watts to Volts (given Current) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#watts-to-volts-given-current): Convert Watts to Volts (given Current).
[Watts to Amps (given Voltage) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#watts-to-amps-given-voltage): Convert Watts to Amps (given Voltage).
[Volts to Watts (given Resistance) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#volts-to-watts-given-resistance): Convert Volts to Watts (given Resistance).
[Amps to Watts (given Resistance) Converter](https://capytoolkit.com/tools/math/ohms-law/conversions/#amps-to-watts-given-resistance): Convert Amps to Watts (given Resistance).

## Concept Guides
[LED Current-Limiting Resistor Calculation](https://capytoolkit.com/tools/math/ohms-law/led-resistor-calculation/): How to calculate a current-limiting resistor for any LED. Step-by-step: supply voltage, forward voltage, target current, E-series rounding, and GPIO limits.
[Wire Gauge, Resistance, and Current Capacity](https://capytoolkit.com/tools/math/ohms-law/wire-gauge-current-capacity/): AWG wire resistance per metre, voltage drop using V = I × R, current-carrying capacity limits, and power loss in DC cable runs. Worked examples for 12V and 5V circuits.
[Designing Voltage Dividers for Sensor Circuits](https://capytoolkit.com/tools/math/ohms-law/voltage-divider-design/): How to design voltage dividers for ADC inputs and sensor bias: R1/R2 calculation, Thevenin equivalent, 10x stiffness rule, tolerance budget, and worked examples.
[Sizing a Power Supply for Your Circuit](https://capytoolkit.com/tools/math/ohms-law/power-supply-sizing/): How to size a power supply: sum load currents per rail using I = P/V, add inrush margin, and choose between regulated linear and switching supplies.
[PCB Trace Current Capacity and Ohm's Law](https://capytoolkit.com/tools/math/ohms-law/pcb-trace-current-capacity/): PCB trace resistance using R = ρL/(WT), IPC-2221 trace width tables, temperature rise calculations, and via current capacity for power and motor driver layouts.
[Calculate Ohm's Law: V, I, and R for Beginners](https://capytoolkit.com/tools/math/ohms-law/ohms-law-for-beginners/): Enter any two of voltage, current, and resistance into the calculator above and get the third instantly, with the water analogy, a worked example, and multimeter verification steps to check your own circuit.
[Measuring Battery Internal Resistance with Ohm's Law](https://capytoolkit.com/tools/math/ohms-law/battery-internal-resistance/): How to measure battery internal resistance using R = (OCV - Vterm) / I. Typical ranges for AA alkaline, 12V lead-acid, and 18650 lithium cells, and what the results mean.

## Ohm's Law & Power Calculator Reference
[Ohm's Law Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#ohms-law-formula): Ohm's Law V = IR defines voltage, current, and resistance for any DC resistive circuit. Definition, three forms, units, and worked examples.
[Watt's Law Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#watts-law): Watt's Law P = VI defines electrical power for any DC circuit. Formula derivation, three forms, worked examples, AC power factor, and fuse sizing.
[Power Dissipation Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#power-dissipation-formula): P = I²R and P = V²/R calculate resistor wattage, wire heating, and motor copper losses. Derivation, derating rules, AWG resistance values, and I²t protection.
[Voltage Divider Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#voltage-divider-formula): Voltage divider formula Vout = Vin × R2/(R1+R2) with Thevenin equivalent, load effect, 10x stiffness rule, R1/R2 derivation, and ADC reference design.
[Series Resistance Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#series-resistance-formula): Series resistance formula R = R1 + R2 + ... with voltage drop calculations, LED series strings, and cable and connector resistance effects on DC circuits.
[Parallel Resistance Formula](https://capytoolkit.com/tools/math/ohms-law/reference/#parallel-resistance-formula): Parallel resistance formula 1/R = 1/R1 + 1/R2 with product-over-sum shortcut, E-series combinations for non-standard values, and I2C pull-up bus sharing.

## Ohm's Law & Power Calculator: Code Examples
[Ohm's Law Measurements on Arduino](https://capytoolkit.com/tools/math/ohms-law/code-examples/#arduino-ohms-law): Use Arduino analogRead() to measure voltage and resistance with Ohm's Law. Voltage divider ohmmeter, shunt current sensing, and power calculation sketches with code.
[Ohm's Law Calculations in Python](https://capytoolkit.com/tools/math/ohms-law/code-examples/#python-ohms-law): Solve Ohm's Law in Python with a four-variable solver function, LED resistor sizing with E24 rounding, and a multi-rail power budget script. No external packages required.
[Verifying Ohm's Law in LTSpice](https://capytoolkit.com/tools/math/ohms-law/code-examples/#ltspice-circuit-simulation): How to verify Ohm's Law in LTSpice with .op and .dc SPICE directives. Single-resistor .op netlist, V-I sweep plotting, LED + resistor simulation with a diode model.

## Multimeter Reference
[Fluke 117 Multimeter: Ohm's Law Measurements](https://capytoolkit.com/tools/math/ohms-law/fluke-117/): How to take voltage, current, and resistance readings with the Fluke 117 for Ohm's Law calculations. True RMS, AutoVolt, LoZ mode, and fuse protection explained.
[Klein Tools MM600 Multimeter: Ohm's Law Measurements](https://capytoolkit.com/tools/math/ohms-law/klein-tools-mm600/): How to use the Klein Tools MM600 for voltage, current, and resistance measurements for Ohm's Law. Auto-ranging 1000V, CAT IV 600V, and drop test durability explained.
[Klein Tools MM400 Multimeter: Ohm's Law Measurements](https://capytoolkit.com/tools/math/ohms-law/klein-tools-mm400/): How to use the Klein Tools MM400 for voltage, current, and resistance in Ohm's Law calculations. Auto-ranging, 40MΩ resistance, CAT III 600V, and five-year warranty explained.
[Milwaukee 2217-20 Multimeter: Ohm's Law Measurements](https://capytoolkit.com/tools/math/ohms-law/milwaukee-2217-20/): How to use the Milwaukee 2217-20 for Ohm's Law voltage, current, and resistance measurements. Lo-Z mode, True RMS, one-hand dial design, and five-year warranty explained.
[AstroAI 6000 Multimeter: Ohm's Law Measurements](https://capytoolkit.com/tools/math/ohms-law/astroai-6000/): How to use the AstroAI 6000-Count multimeter for Ohm's Law measurements. 6000-count display, True RMS, NCV detector, rechargeable battery, and hobbyist usability notes.